As light emitting diode (LED) luminaires increase in popularity, there is an increased desire to improve their operation and reduce manufacturing costs. One way that this has been done involves the use of a buck regulator to drive the LEDs in a luminaire. A buck regulator can help drive LEDs at higher current levels, thus increasing the lumens-per-LED output, and optionally reducing overall manufacturing costs.
However, a problem with the use of buck regulators to drive LED luminaires is that they depend on series LED strings to function. When it is desired to skip an LED in a string (i.e., selectively operate the LEDs), existing systems may use transistors to bypass selected LEDs, or they may use multiple buck regulators. The use of transistors may be sufficient when only a single LED is bypassed, but bypassing multiple LEDs can cause catastrophic voltage transients across the remaining LEDs, resulting in complete failure of the LED string. This risk is increased when high frequency controls are required, as a quick shift in load becomes more likely. The use of multiple buck regulators increases the cost and complexity of the luminaire's control system.
This document describes methods and systems that are directed to solving at least some of the issues discussed above.